In introductory economics courses, we are taught that every decision involves trade-offs. With that in mind, we should be wary of the simple-minded arguments in defense of unions that extend everywhere from the streets of Chicago to O’Donovan Hall.

Sketching a basic history of organized labor helps to illuminate the past importance — and present condition — of modern American unions.

Without a doubt, they helped to build America’s middle class into the envy of the world. It was unions that helped create minimum wages and maximum hours, ended many abusive labor practices and extended health care and pensions, however modest, to millions of American employees.

Over the past few decades, however, unions have seen their membership fall because of the conversion of the economy from manufacturing to services, coupled with government policies that have become less favorable to worker organization.

More and more states, particularly in the fast-growing South and West, have passed “right-to-work” laws, although that clever phrase does not accurately describe what is really an attempt to weaken unions by allowing workers to receive the benefits of collective bargaining without helping to fund their unions’ activities.

Though most employees in the private sector are no longer members of a union, the public sector has remained highly organized. Although membership has fallen, organized labor remains a potent political force, particularly within the Democratic Party.

Nevertheless, unions are under attack. Wisconsin’s controversial law targeting public-sector workers was perhaps the most brazen assault, eliminating the deduction of union dues from paychecks, requiring yearly votes among employees on the unions’ continued existence and chipping away at the right to bargain for anything except wage increases.

For people who believe, as I do, that America is at its best when everyone works together toward a common purpose, the attacks on organized labor are troublesome. The late Sen. Ted Kennedy (D-Mass.) said it best: “What is it about working men and women they find so offensive?”

Yet in rallying around working families, people sometimes become too starry eyed about the actual effectiveness of unions. When it acts responsibly, labor is a force for good. When unions focus instead on narrow issues of self interest, they emulate the same selfishness they purport to decry. The Chicago teachers’ strike is a case in point.

Across the country, teachers are not paid commensurate to their critical role in society. The profession is given neither the respect nor the recognition it deserves. But while many individual teachers go to heroic ends to make their students successful, their unions all too often stand in the way of progress.

Chicago Mayor Rahm Emanuel, not a conservative by any measure, proposed a fair contract that included a whopping 16 percent pay increase in exchange for more comprehensive accountability, including detailed evaluations of classroom performance.

But for the Chicago Teachers Union, 16 percent wasn’t enough. They demanded a bigger raise and weaker evaluating criteria, and, when their demands weren’t met, they went on strike.

We tend to view labor disputes in a vacuum. Management wants one things, labor wants something different; the fight is between them. That ignores the impact that union contracts have beyond the bargaining table.

To fund a 16 percent raise, Chicago will have to hike taxes and slash spending for other important services. And if the union prevails on weaker accountability standards, 350,000 Chicago public-school students will pay the price.

The underpaid food service workers here at Georgetown have more moral authority than the Chicago teachers — who are among the highest paid in the nation — but the union contract at Leo’s also imposes indirect costs.

By all accounts, cafeteria staffers were treated poorly by their employer, Aramark Higher Education, before the workers organized and affiliated with UNITE HERE. And if the recent allegations that Aramark continues to mistreat workers are true, the union should make full use of relevant local and federal labor laws to force the company into compliance.

A union contract gives workers better pay and more generous benefits, increasing the cost of running the dining hall. To balance higher labor costs, it would make sense for Aramark to minimize other expenses or raise the price of meals.

Personally, I’m more than willing to forgo weekday “make-your-own pizza” if it means that cafeteria workers — who get up before dawn, often don’t get home until after sundown and work a low-wage job in between — have more money in their pockets and more dignity in their work.

But we must be honest about the costs and benefits of unions. After all, another lesson of economics is that there is no such thing as a free lunch.

EVAN HOLLANDER is a junior in the School of Foreign Service. He is senior sports editor of The Hoya.